The role of proprioceptive afferents in the control of respiratory muscles.

Building largely on the results of previous studies of motor control in respiration the role of proprioceptive control of respiratory movements is discussed with particular reference to the significance of the following points: (i) The co-activation of fusimotor and alpha motoneurons in load compensation and in the control of velocity and force of the respiratory movements. (ii) The convergence onto the same intercostal spindle of fusimotor fibres for respiratory movements and for postural activity. (iii) The difference between proprioceptive control of intercostal muscles on the one hand and the diaphragm on the other, and of the control of the phrenic motoneuron pool exerted by intercostal proprioceptors. (iv) The cerebellar control both of the fusimotor-alpha balance between the indirect drive of the intercostal motoneurons and of the responsiveness of the phrenic motoneuron pool to respiratory and reflex influences. (v) Results suggesting spinobulbar reflex effects on the control of rate and depth of respiration from muscle and joint receptors of the thoracic wall.